To me, beautiful code is code that is so simple and so clear that it's obviously correct. This code took me too long to understand (realize it has to be read right to left, remember that uc defaults to $_, mentally pass the array from one map to the other...). I'd change it.

a reasonably intelligent person can correctly understand that 'function' is acting on $a and $b to produce result $x, for example. Then go find out what 'function' does.

If a reasonably intelligent person can't even get that from the code without knowledge of all sorts of arcane idiosyncracies of the language, then we mustn't be surprised when IT managers reject Perl with that tired old refrain about it being unreadable